Withholding Tax for other countries

Hi SAP Experts,

We are doing implementation to a Company situated in Country Kenya for which Tax procedure has not been defined by the SAP. To this company Withholding tax provisions are appliable as applicable to India. We have configured everything and updated in the Vendor master data all the tax codes.

At the time of Vendor Invoice its not calculating tds automatically. without these tax line items posting is happening.

But when we enter manually the Base amount as well as tax amount line items are coming properlty i.e expenditure a/c Dr Vendor Cr Withholdin tax payable Cr...

What would be the problem? Can we take help from SAP or anything we need to do from our end?